Known dishwashers include a cabinet having an access door hinged at its lower end to pivot on a horizontal axis and open outwardly from the cabinet. The cabinet includes a wash chamber, and lower and upper dishwashing racks are vertically mounted within the wash chamber. The racks can be slidably withdrawn outwardly through an access opening.
Washing systems utilized in known dishwashers include first level, second level, and third level type systems. A first level washing system sprays water from below the lower rack up into dishes located on the lower rack. A typical first level washing system includes a rotatable arm mounted below the lower rack and having a plurality of spray openings. The spray openings face upward towards the lower rack. In operation, as the rotatable arm rotates water is supplied to the arm and is sprayed out from the arm through the spray openings.
A second level washing system, in addition to first level washing, sprays water to the underside of the upper rack. A typical second level washing system includes a retractable tower which, when supplied with water, extends through and at least partially above the lower rack. The retractable tower includes openings in its side surface near its uppermost end, and water under pressure flows through the openings and up into dishes and cups located on the upper rack.
A third level washing system, in addition to first and second level washing, sprays water above the upper rack. A typical third level washing system includes a rotatable arm mounted above the upper rack, e.g., to the top wall of the tub, and has a plurality of spray openings. The spray openings face downward towards the upper rack. In operation, as the rotatable arm rotates, water is supplied to the arm and is sprayed out from the arm through the spray openings and into the dishes and cups on the upper rack.
Of course, a dishwasher including a third level washing system typically is more expensive to manufacture, in terms of both component and assembly costs, than a dishwasher including first or second level washing systems. It would be desirable to reduce the cost of third level washing systems since such systems are believed to provide the most effective washing.
Further, with respect to dishwashers incorporating third level washing systems, such dishwashers typically utilize more water during a wash cycle than dishwashers with just first or second level washing systems. Therefore, a dishwasher including a third level washing system typically is more expensive to operate than a dishwasher including just first or second level washing systems. It would be desirable to reduce the operating cost of third level washing systems.
In addition to the costs associated with known third level dishwashing systems, another concern relates to blockage of spray openings in the tower under the upper rack. The tower typically has large diameter spray openings to prevent soil from blocking the spray openings. To spray water on the underside of the upper rack for second level washing, however, smaller diameter spray openings generally are preferred. With small diameter tower openings, the magnitude of noise generated when water flows onto the dishwasher door and tub is lower than the magnitude of noise which results with larger openings. Particularly in a residential dishwasher which typically is located in the living area of a residence, it is desirable to decrease the magnitude of noise generated by the dishwasher.